At least one hard disk drive (HDD) is used in almost all computer system operations. In fact, most computing systems are not operational without some type of HDD to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the HDD is a device which may or may not be removable, but without which the computing system will generally not operate.
In an HDD, there may be a read and write head that flies over a disk with a clearance. Such clearance may fluctuate causing inconsistencies in HDD operations especially when the read and write head contacts the magnetic disk. To compensate, control systems in the HDD may measure changes in the clearance between the disk and the read and write head.